Multilayer polyurethane protective films

ABSTRACT

A multilayer protective film comprising a first layer, a second layer and a PSA layer. The first layer at least comprises a polyester-based polyurethane, a polycarbonate-based polyurethane or a combination or blend of both. The second layer at least comprises a polycaprolactone-based thermoplastic polyurethane. The PSA layer comprises a pressure sensitive adhesive. One major surface of the first layer is bonded to one major surface of the second layer, and the PSA layer is bonded to an opposite major surface of the second layer such that the second layer is sandwiched between the first layer and the PSA layer.

TECHNICAL FIELD

The present invention relates to multilayer films used to protect asurface, in particular, to such films used to protect surfaces (e.g., apainted surface) of a vehicle (e.g., an automobile, aircraft,watercraft, etc.) and, more particularly, to such a multilayerprotective film backed by a pressure sensitive adhesive and having apolyurethane layer on top of a thermoplastic polyurethane layer. Thepresent invention also relates to a vehicle, or a body portion thereof,that is protected by the multilayer film as well as a method for makingthe multilayer protective film.

BACKGROUND ART

Multilayer films that include one or more layers of a polyurethanematerial are known. Some of these films are disclosed in U.S. Pat. Nos.6,607,831, 5,405,675, 5,468,532 and 6,383,644 as well as International(PCT) Patent Application No. PCT/EP93/01294 (i.e., Publication No. WO93/24551). Some of these films have been used in surface protectionapplications. For example, actual film products that have been used toprotect the painted surface of selected automobile body parts includemultilayer films manufactured by 3M Company, St. Paul, Minn., under theproduct designations Scotchcal™ high performance protective filmPUL0612, PUL1212 and PUL1212DC. Each of these 3M Company film productsincludes a thermoplastic polyester polyurethane layer that is backed bya pressure sensitive adhesive (PSA) on one major surface and covered bya water-based polyester polyurethane layer on the opposite majorsurface.

The present invention is an improvement in such multilayer protectivefilm technology.

SUMMARY DISCLOSURE

In accordance with one aspect of the present invention, a multilayerprotective film is provided that comprises a first layer, a second layerand a PSA layer. The first layer consists of, consists primarily of, orat least comprises a solvent-based or water-based polyurethane. Thepolyurethane is a polyester-based polyurethane, a polycarbonate-basedpolyurethane or a combination or blend of both. The second layerconsists of, consists primarily of, or at least comprises apolycaprolactone-based thermoplastic polyurethane. The PSA layercomprises a pressure sensitive adhesive, and preferably one that istacky at room temperature. One major surface of the first layer isbonded to one major surface of the second layer, and the PSA layer isbonded to an opposite major surface of the second layer such that thesecond layer is sandwiched between the first layer and the PSA layer.

It can be desirable for the polyurethane used in the first layer to beat least a slightly crosslinked polyurethane but not a heavilycrosslinked or thermoset polyurethane. The polyurethane can be areaction product of constituents comprising one or more polyols and oneor more diisocyanates. Preferably, a mixture of one or morediisocyanates and one or more triisocyanates is used. Improvedperformance has been obtained by using aliphatic materials in thepresent multilayer film. For example it can be desirable for the presentfilm to use an aliphatic polyurethane, an aliphaticpolycaprolactone-based thermoplastic polyurethane or both. In making thepolyurethane, it can also be desirable to use aliphatic components.

A film according to the present invention can be sized and shaped toconform to a surface of a vehicle body part.

In accordance with another aspect of the present invention, a vehiclebody part is provided that has a painted surface protected by amultilayer protective film as described herein.

In accordance with an additional aspect of the present invention, avehicle (e.g., an automobile, aircraft, watercraft, etc.) is providedthat includes such a protected body part.

In accordance with a further aspect of the present invention, a methodof making a multilayer protective film is provided. The method comprises(a) forming a first layer; (b) forming a second layer; (c) forming a PSAlayer comprises a pressure sensitive adhesive; (d) bonding one majorsurface of the first layer to one major surface of the second layer; and(e) bonding the PSA layer to an opposite major surface of the secondlayer. The first layer consists of, consists primarily of, or at leastcomprises a solvent-based or water-based polyurethane. The polyurethaneis a polyester-based polyurethane, a polycarbonate-based polyurethane ora combination or blend of both. The second layer consists of, consistsprimarily of, or at least comprises a polycaprolactone-basedthermoplastic polyurethane. The PSA layer comprises a pressure sensitiveadhesive, and preferably one that is tacky at room temperature. Thelayers are bonded together so that the second layer is sandwichedbetween the first layer and the PSA layer.

The opposite major surface of the second layer can be corona treatedbeforehand to improve the bond with the PSA layer.

The method step of forming the first layer can further comprise castingor otherwise coating an aqueous-based polyurethane dispersion or asolvent-based polyurethane solution onto a releasable carrier web orliner. The method step of forming the second layer can further compriseextruding the polycaprolactone-based thermoplastic polyurethane at anelevated temperature through a die to form the second layer. The methodstep of bonding the first layer to the second layer can also furthercomprise laminating the one major surface of the first layer to the onemajor surface of the second layer, after the second layer is extrudedand while at least the one major surface of the second layer is, or boththe second layer and the first layer are, at an elevated temperaturethat is sufficiently higher than room temperature to facilitate adequatebonding between the first layer and the second layer.

The method step of bonding the first layer to the second layer canalternatively comprise heating at least the one major surface of thesecond layer, at least the one major surface of the first layer, or theone major surface of both the first layer and the second layer to anelevated temperature and laminating the one major surface of the firstlayer to the one major surface of the second layer after the secondlayer is extruded, cast or coated onto a releasable liner, or otherwiseformed. The heating can occur before and/or during the laminating. Theelevated temperature is sufficiently higher than room temperature tofacilitate adequate bonding between the first layer and the second layerduring the laminating. This method of bonding can be useful when atleast the one major surface of the first layer and the one major surfaceof the second layer is at about room temperature or at least at atemperature that is too low to facilitate adequate bonding between thefirst layer and the second layer.

Other features and advantages of the present invention will be apparentfrom the following description of embodiments thereof and from theclaims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 a cross-sectional view of a multilayer film according to thepresent invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Although the present invention is herein described in terms of specificembodiments, it will be readily apparent to those skilled in this artthat various modifications, re-arrangements, and substitutions can bemade without departing from the spirit of the invention.

A multilayer protective film, according to the present invention,comprises a first or PU layer, a second or TPU layer and a PSA layer.The PU layer consists of, consists primarily of, or at least comprises asolvent-based or water-based polyurethane, the polyurethane is apolyester-based polyurethane, a polycarbonate-based polyurethane or acombination or blend of both. The water-based polyurethane can be madefrom an aqueous-based polyurethane dispersion (i.e., PUD), and thesolvent-based polyurethane can be made from a solvent-based polyurethanesolution (i.e., PUS). It can be preferable to use PUDs, because of theelimination of the volatile solvents typically associated with usingPUSs. The TPU layer consists of, consists primarily of, or at leastcomprises a polycaprolactone-based TPU (i.e., thermoplasticpolyurethane). The PSA layer comprises a pressure sensitive adhesive,and preferably one that is tacky at room temperature. The PU layer isbonded to one major surface of the TPU layer and the PSA layer is bondedto an opposite major surface of the TPU layer such that the TPU layer issandwiched between the PU layer and the PSA layer.

Superior results have been obtained with a multilayer film, according tothe present invention, that includes a PUD layer that uses apolycarbonate-based polyurethane or a polyester-based polyurethane. Itis believed that superior results would likewise be obtained with a PUSlayer that uses a polycarbonate-based polyurethane or a polyester-basedpolyurethane. It has also been found that a PUD layer that uses apolycarbonate-based polyurethane exhibits results that are superior tothose obtained with a PUD layer that uses a polyester-basedpolyurethane. It is believed that superior results would likewise beobtained with a PUS layer that uses a polycarbonate-based polyurethaneas compared to a PUS layer that uses a polyester-based polyurethane.

The polyurethane can be the reaction product of one or more polyolsegments and one or more diisocyanate segments. It is desirable for oneor more triisocyanate segments to be used with the diisocyanate. It hasbeen found desirable to use up to abut 10%, based on the total weight ofthe reaction components, of triisocyanate segments with thediisocyanate. The polyol is a polyester polyol, a polycarbonate polyolor a combination of both. Superior results have been obtained using apolycarbonate polyol. It has also been found desirable to use adiisocyanate such as, for example, isophorone diisocyanate,bis(4-isocyanato-cyclohexyl) methane or a combination of both.

Improved performance has been obtained by using aliphatic materials inthe present multilayer film such as, for example, an aliphaticwater-based polyurethane, an aliphatic polycaprolactone-basedthermoplastic polyurethane or both. It is believed that improvedperformance would likewise be obtained by using aliphatic materials in asolvent-based system such as, for example, an aliphatic solvent-basedpolyurethane. Thus, in making the polyurethane, it can be desirable touse one or a combination of aliphatic polyols, aliphatic diisocyanatesand aliphatic triisocyanates. Superior results have been obtained, forexample, using an aliphatic polycarbonate polyol in a PUD layer. It isbelieved that superior results would also be obtained, for example,using an aliphatic polycarbonate polyol in a PUS layer.

It has been found that it can be desirable for the present multilayerfilm to use a polyurethane that is at least a slightly crosslinkedpolyurethane but not a thermoset polyurethane. As used herein, aslightly crosslinked polyurethane is one that can exhibit at leastenough melting or at least enough softening, when heated to asufficiently high temperature, to form a bond that is strong enough topass the “Tape Snap Adhesion Test” when a layer of the polyurethane islaminated to a layer of the thermoplastic polyurethane. In contrast, asused herein, a thermoset polyurethane is one that is so heavilycrosslinked that it does not exhibit a sufficient amount of melting orsoftening when heated. That is, a thermoset polyurethane will generallyburn rather than melt or soften and would not form a bond that is strongenough to pass the “Tape Snap Adhesion Test” when a layer of thethermoset polyurethane is laminated to a layer of the thermoplasticpolyurethane, even when the thermoplastic polyurethane is heated beforeit is laminated.

The present multilayer film can be easier to apply when the PSA layerconsists of, consists primarily of or at least comprises a pressuresensitive adhesive that is tacky at room temperature (i.e., around 75°F. (22-24° C.)).

The present inventive multilayer film is typically transparent, andpossibly even translucent, for paint protection applications. Thepresent inventive multilayer film may also be transparent, translucentor even opaque for other surface protection or enhancement applications.For some applications, it may be desirable for the present multilayerfilm to be colored. The present film could be colored such as, forexample, by one or more of its layers further comprising a pigment orother coloring agent.

When used, for example, as a paint protection film, it has beendesirable for the present multilayer film to be sized and shaped toconform to the surface to be protected, before the film is applied.Pre-sized and shaped pieces of the present multilayer film can becommercially desirable for protecting the painted surface of variousbody parts of a vehicle such as, for example an automobile, aircraft,watercraft, etc., especially those portions of the vehicle body (e.g.,the leading edge of the front hood and other leading surfaces, rockerpanels, etc.) that are exposed to such hazards as flying debris (e.g.,sand, rocks, etc.), insects, or the like.

Method of Making

A method of making a multilayer protective film, according to thepresent invention comprises: (a) forming a first or PU layer; (b)forming a second or TPU layer; (c) forming a PSA layer; (d) bonding onemajor surface of the PUD layer to one major surface of the TPU layer;and (e) bonding the PSA layer (e.g., by corona treating and thermallylaminating, coating or otherwise applying the pressure sensitiveadhesive so as to adhere) to an opposite major surface of the TPU layer,with the TPU layer being sandwiched between the PU layer and the PSAlayer. The PU layer can consists of; consists primarily of or at leastcomprises a polyurethane made from an aqueous-based polyurethanedispersion (i.e., PUD) or a polyurethane made from a solvent-basedpolyurethane solution. The polyurethane can be a polyester-basedpolyurethane, a polycarbonate-based polyurethane or a combination ofboth. The TPU layer consists of, consists primarily of or at leastcomprises a polycaprolactone-based TPU (i.e., thermoplasticpolyurethane). The PSA layer comprises a pressure sensitive adhesive,and preferably one that is at least somewhat tacky at room temperature.

In the practice of the method of the present invention, the PU layer maybe formed using conventional practices such as, for example, by theaqueous dispersion or solvent solution mixture being cast or otherwisecoated onto a releasable carrier web or liner. Those skilled in the artare capable of casting or otherwise coating the aqueous dispersion orsolvent solution mixture of the present invention onto a releasablecarrier web using known techniques. Suitable carriers may include filmssuch as biaxially oriented polyester and papers that may be coated orprinted with a composition that will enable release from thepolyurethane compositions. Such coatings include those formed frompolyacrylics, silicone, and fluorochemicals. The aqueous dispersion orsolvent solution mixture can be coated onto a carrier web usingconventional equipment known by those skilled in the art such as knifecoater, roll coaters, reverse roll coaters, notched bar coaters, curtaincoaters, roto-gravure coaters, rotary printer and the like. Theviscosity of the aqueous or solvent mixture can be adjusted to the typeof coater used. The water or solvent in the coated mixture is thenremoved such as, for example, by drying.

The PU layer can be formed, for example, by casting or otherwise coatingan aqueous PUD (i.e., polyurethane dispersion) or solvent PUS (i.e.,polyurethane solution) onto a readily releasable carrier web or liner(e.g., a polyester carrier web) having a smooth surface. By using such acarrier web or liner having a smooth surface on which to apply theaqueous PUD or solvent PUS, the resulting PU layer can exhibit anexposed major surface with the appearance of having been cast onto asmooth major surface of a releasable carrier web or liner, dried orotherwise cured and the carrier web removed. In contrast, if the PUlayer is open air dried or cured such as, for example, by casting orcoating the PU layer onto the one major surface of the TPU layer, thenthe exposed major surface of the PU layer would not exhibit the samesmooth appearance.

The TPU layer can be formed by extruding the polycaprolactone-based TPU(i.e., thermoplastic polyurethane) at an elevated temperature through anextrusion die. The TPU layer may also be formed by casting or otherwisemolding (e.g., injection molding) the polycaprolactone-based TPU intothe shape desired.

The PU and TPU layers can be bonded together, for example by laminatingthe layers at an elevated temperature and pressure. For example, onemajor surface of the PU layer can be cold laminated under pressure toone major surface of the extruded TPU layer, while at least the onemajor surface of the TPU layer is, or both the TPU layer and the PUlayer are, at an elevated temperature that is sufficiently high enoughto facilitate adequate bonding between the PU layer and the TPU layer.As used herein, cold laminating refers to the layers being laminatedtogether between two nip surfaces in about a room or ambient temperatureenvironment (i.e., the layers are not kept in an intentionally heatedenvironment during the laminating process). The nip surfaces may be twonip rollers, a stationary nip surface (e.g., a low friction surface of aflat or curved plate) and a nip roller, or two stationary nip surfaces.The laminating process may even be performed in a below ambienttemperature environment (i.e., the layers are intentionally cooledduring the laminating process). For example, one or both of the nipsurfaces can be chilled to a temperature below ambient, in order to coolthe exposed major surfaces of the polyurethane layers (i.e., the majorsurfaces the nip surfaces contact). The use of such chilled surfaces caneliminate, or at least help reduce, warping of the layers resulting fromthe laminating process. At the same time, the major surfaces that makecontact at the interface between the polyurethane layers remain at theelevated temperature long enough to be sufficiently bonded together bythe laminating pressure exerted by the nip surfaces. Such coldlaminating can be accomplished by laminating the newly extruded TPUlayer directly onto a preformed PU layer, while the TPU material stillretains significant heat from the extrusion process. The PU layer istypically still releasably bonded to the carrier web or liner, toprovide additional structural strength.

Alternatively, one major surface of the PU layer can also be bonded toone major surface of the extruded TPU layer by using a hot laminatingprocess. With this process, the initial temperature of both the PU layerand the TPU layer is about room temperature or at least a temperaturethat is too low to facilitate adequate bonding between the PU layer andthe TPU layer. Then, at least the one major surface of the TPU layer, atleast the one major surface of the PU layer, or the one major surfacesof both the PU layer and the TPU layer are heated to an elevatedtemperature that is sufficiently higher than room temperature tofacilitate adequate bonding between the PU layer and the TPU layer underthe laminating pressure. With the hot laminating process, the layers areheated before or during the application of the laminating pressure. Whena hot laminating process is used, a major surface of the TPU layer istypically releasably laminated to a readily releasable carrier web orliner (e.g., a polyester carrier web) directly after the TPU layer isextruded, in order to provide the freshly extruded TPU layer withadditional structural support.

Acceptable minimum temperatures and pressures for bonding the layerstogether, using either the cold or hot laminating process, have includeda temperature of at least about 200° F. (93° C.) and a pressure of atleast about 15 lb/in² or psi (10.3 N/cm²).

To facilitate or at least improve bonding between the TPU layer and thePSA layer it can be desirable to corona treat (e.g., air or N₂ coronatreatment) and thermally laminate the major surface of the extruded TPUlayer to be bonded to the PSA layer. To accomplish this, the majorsurface of the TPU layer, which is not in contact with the PU layer, isexposed and then corona treated. If a hot laminating process is used(i.e., the TPU layer is extruded onto a releasable carrier web orliner), the carrier web or liner must first be stripped off of the TPUlayer.

Referring to FIG. 1, an exemplary multilayer film 10, in accordance withthe principles of the present invention includes at least a first or PUlayer 12, a second or TPU layer 14 and a third or PSA layer 16. Anoptional releasable carrier web or liner 18 can be releasably bonded soas to protect the surface of the PU layer 12. It is desirable for thefilm 10 to also include another release liner 20 releasably bonded so asto protect the PSA layer 16.

Tape Snap Adhesion Test

This test provides an indication of how well a film construction remainstogether after exposure to various conditions. A sample of thepressure-sensitive adhesive coated polyurethane construction is adheredto a painted panel and aged for 24 hours at room temperature. A separatepanel is then aged using each one of the conditions listed below.

-   -   Water Immersion—panel immersed in 40° C. water bath for 7 days.    -   Fog chamber—panel aged on a rack at about 30 degree angle and        exposed for 7 days at 38° C. in a chamber with 100% condensation    -   Salt spray—panel placed on a rack at about 30 degree angle and        exposed for 7 days at 35° C. using a 5% sodium chloride solution        in a salt fog chamber

After aging, the panel is dried if needed, and then conditioned at roomtemperature (about 22° C.) for 24 hours. The film is then cross-hatchedwith a razor blade to form a grid of about 20 squares each measuringabout 1 mm by 1 mm. A strip of 610 Tape (available from 3M Company, St.Paul Minn.) is adhered over the cross-hatched area using firm fingerpressure, and then the tape is snapped off with a quick pull. The sampleis rated as Pass (no delamination of any squares the film or blisteringof the film is observed after tape is removed) or Fail (at least onesquare is removed with the tape or blistering is observed after tape isremoved).

Staining and Discoloration Test

This test is an evaluation of the amount of discoloration a filmexhibits when exposed to different automotive fluids. The film or thepolyurethane construction, is adhered to a test panel. A drop of fluidis placed on the film and aged for 24 hours. The fluid is cleaned withmineral spirits and examined visually for discoloration for each of thefluids. Pass indicates no discoloration was visually observed and failindicates that discoloration was observed. The panels can also bemeasured using a colorimeter to determine the discoloration. Test fluidswere grease, tar, transmission fluid, motor oil, fuel oil, diesel oil,gear oil, and SUNOCO lub/grease.

EXAMPLES 1-3

An aqueous polyurethane coating dispersion was prepared by mixing 83.78grams of a water-based, polycarbonate-based polyurethane dispersion(ALBERDINGK U933 available from Alberdingk Boley, Inc., Charlotte,N.C.), 0.03 grams of a pH adjuster (aminomethyl propanol available asAMP-95 from Angus Chemical Co., Buffalo Grove, Ill.), 0.19 grams of asulfosuccinate type anionic surfactant (Triton GR-7M available from DowChemical Company, Midland Mich.), 8.47 grams of butyl carbitol(available from Eastman Chemical Co.), 1.08 grams of 2-ethylhexylα-cyano-α,β′-diphenylacrylate UV light absorber, and 0.45 grams of alight stabilizer (hindred amine light stabilizer based on aminoetherfunctionality available as TINUVIN 123 from Ciba Specialty Chemicals).The dispersion was diluted with do-ionized water to maintain theviscosity between 70 cps and 180 cps. Just prior to coating, 1.30% of acrosslinker (aziridine crosslinker available as NEOCRYL CX-100 fromNeoresins, Inc., Waalwijk, Netherlands, a business unit of DSM) wereadded under agitation. The dispersion was coated to a thickness of about50 microns onto a polyester carrier web. The coated dispersion was driedand cured sequentially in separate ovens for about 0.5 minutes each. Theoven temperatures were set at 121° C., 149° C., and 163° C. for thefirst, second, and third ovens, respectively. The resulting clear filmwas about 11-12 microns thick. A thermoplastic polyurethane(caprolactone based polyurethane available as TECOFLEX CLA 93A-V fromNoveon) was extruded to a thickness of 150 microns and the extrudate waslaminated to the clear film between the nip of a backup roll against thechill roll. After the laminate was cooled, the other side of thethermoplastic polyurethane film was air corona treated at 1 kilowattsand thermally laminated to an acrylic pressure-sensitive adhesive on apaper release liner at 121° C. (250° F.) to form a polyurethaneconstruction.

Examples 2 and 3 were prepared in the same manner except that thethermoplastic polyurethane films were 200 microns and 300 microns thick,respectively.

The polyurethane constructions for each of the examples were tested foradhesion of the clear coat to the extruded thermoplastic polyurethaneafter aging according to the Tape Snap Adhesion Test described above.All of the samples passed. The polyurethane construction also passed theStaining and Discoloration Test with all of the fluids.

EXAMPLE 4

A polyurethane construction was prepared according the procedure ofExample 1 except the dispersion used for the clear film had 8.28 gramsof butyl carbitol, 0.39 grams of TINUVIN-123 light stabilizer, and 0.26grams of surfactant (silicone based surfactant available as BYK-331 fromByk-Chemie, Wallingford, Conn.). The resulting construction passed theTape Snap Adhesion Test after all three aging conditions, as well as theStaining and Discoloration Test with all of fluids.

EXAMPLE 5

A thermoplastic caprolactone-based polyurethane (Tecoflex CLA 93A-V) wasextruded to a thickness of about 150 microns onto a polyester carrierweb and cooled to room temperature. A clear film, prepared from thewater based polyurethane dispersion described in Example 1, waslaminated to the thermoplastic polyurethane film using a nip roll set at121° C. with a nip pressure set at 30 psi. The polyester carrier web onthe extruded thermoplastic polyurethane was removed, the surface ofthermoplastic polyurethane was air corona treated at 1 kilowatts, andthermally laminated to an acrylic pressure-sensitive adhesive on a paperrelease liner at 121° C. (250° F.). The resulting construction passedthe Tape Snap Adhesion Test after all of the aging conditions, as wellas the Staining and Discoloration Test with all of the fluids.

EXAMPLE 6

A polyurethane construction was prepared according to the procedure ofExample 5 except that the extruded polyurethane film was air coronatreated and laminated to the acrylic pressure-sensitive adhesive first,and then laminated to the clear film. The resulting construction passedthe Tape Snap Adhesion Test after all of the aging conditions as well asthe Staining and Discoloration Test with all of the fluids.

EXAMPLE 7

An aqueous polyurethane coating dispersion was prepared by mixing 89.30grams of a polycarbonate-based polyurethane dispersion (NEOREZ-986available from Neoresins, Inc.), 0.35 grams of TINUVIN-123 lightstabilizer, 0.20 grams of BYK-025 surfactant, 0.05 grams AMP-95 pHadjuster, 0.20 grams of TRITON GR-7M surfactant, 8.5 grams of butylcarbitol, 1.16 grams of 2-ethylhexyl α-cyano-α,β′-diphenylacrylate, and0.20 grams of BYK-331 surfactant. The solution mixture was diluted withde-ionized water and to maintain its viscosity between 100 cps and 200cps. Just prior to coating, 1.78 grams of Neocryl CX-100 were added andthe dispersion was coated to a thickness of about 76 micrometers on athermoplastic polyurethane film. The thermoplastic polyurethane film wasa 150 micrometers thick film formed by extruding a polyester-basedthermoplastic polyurethane. The clear coat was dried and curedsequentially for about one minute in each of three ovens set at 66° C.,107° C., and 141° C. The resulting polyurethane construction had a clearcoat film with a thickness of about 20 micrometers. The construction wasleft at ambient temperature for 48 hours and tested for adhesion of theclear coat to the thermoplastic polyurethane and staining anddiscoloration. The construction passed all of the tests.

EXAMPLE 8

A polyurethane construction was prepared according to the procedure ofExample 1 except that the clear film dispersion was made by mixing 89.18grams of a polyester based polyurethane (NEOREZ 9679 available fromNeoresins, Inc.), 0.02 grams AMP-95 pH adjuster, 0.18 grams of TritonGR-7M surfactant, 9.03 grams of butyl carbitol, 1.07 grams of UV lightabsorber (TINUVIN 1130 available from Ciba Specialty Chemicals) and 0.52grams of light stabilizer (TINUVIN 292 available from Ciba SpecialtyChemicals). The dispersion was coated to a thickness of about 65micrometers wet on a polyester carrier web. After drying and curing, theclear film had a thickness about 18-20 micrometers. The polyurethaneconstruction was tested for adhesion and passed at all aging conditions.

EXAMPLES 9-14

Clear films were prepared according to the procedure of Example 1 exceptthat the polycarbonate-based polyurethane dispersions used and theresulting film thicknesses were as follows:

-   Example 9—NEOREZ-985 available from Noveon—20 micrometers-   Example 10—NEOREZ-9603 available from Noveon—20 micrometers-   Example 11—SOLUCOTE-1026 available from Soluol Chemicals—20    micrometers-   Example 12—ALBERDINGK U930 available from Alberdingk Boley—20    micrometers-   Example 13—ALBERDINGK U933 available from Alberdingk Boley—20    micrometers-   Example 14—ALBERDINGK U911 available from Alberdingk Boley—20    micrometers

All of the clear films passed the stain and discoloration test for allof the fluids.

EXAMPLES 15-17

Polyurethane constructions were prepared according to the procedure ofExample 7 using polyurethane dispersions coated to the thickness shownbelow.

-   Example 15—NEOREZ-9603—5.5 micrometers-   Example 16—ALBERDINGK U933—11 micrometers-   Example 17—ALBERDINGK U911—11 micrometers

All of the constructions of Examples 1 to 17 passed the Tape SnapAdhesion test at all aging conditions as well as the Stain andDiscoloration Test for all fluids.

In Examples 4 and 7, it has been found desirable to remove thesurfactant Byk-331 from the formulation, because it can cause cloudinessin the layer, after the multilayer film is subjected to the 40° C. waterimmersion aging during the Tape Snap Adhesion Test. Otherwise, the useof this surfactant does not appear to result in any other negativeeffect.

EXAMPLE 18

A solvent-based polyurethane solution was prepared with a Part A and aPart B solution. The Part A solution was prepared by combining 50 gramsof the polyester polyol Fomrez-55-225 (from Crompton Corp.), 20 grams ofthe polyester polyol Fomrez-55-112 (from Crompton Corp.), 5 grams of thepolycaprolactone polyol Tone-305 (from Dow Chemicals), 20 grams of themonomer 1,4-butanediol (from BASF), 0.008 grams of the catalystdibutyltin dilaurate (from Air Products, Inc), 2 grams of the UV lightstabilizer Cosorb OSG (from 3M Company), 1 gram of the UV lightstabilizer Tinuvin-292 (from Ciba-Geigy Chemicals), 30 grams of thesolvent propylene glycol methyl ether acetate, 20 grams of the solventbutyl acetate, and 20 grams of the solvent xylene. The Part B solutionwas prepared by combining 75 grams of the dicyclohexylmethanediisocyanate Desmodur W (equivalent weight=132) (from Bayer Corp), 10grams of the aliphatic polyisocyanate, based onhexamethylenediisocyanate, Desmodur N75 (eq wt=255) (from Bayer Corp),and 15 grams of butyl acetate. After Parts A and B are mixed, theresulting solution is coated onto a polyester carrier web and curedaccording to the following profile: 1 minute at 175° F., 1 minute at225° F., 1 minute at 265° F., and 1 minute 285° F. The resulting clearfilm was about 11-12 microns thick. A thermoplastic polyurethane(caprolactone based polyurethane available as TECOFLEX CLA 93A-V fromNoveon) is extruded into a film having a thickness of 150 microns. Oneside of the resulting extruded film is laminated to the clear filmbetween the nip of a backup roll against a chill roll. The other side ofthe thermoplastic polyurethane film is air corona treated at 4 kilowattsand thermally laminated to a layer of acrylic pressure sensitiveadhesive, releasably adhered on a paper release liner, at 190° F. toform the exemplary polyurethane construction.

EXAMPLE 19

A solvent-based polyurethane solution was prepared with a Part A and aPart B. The Part A solution was prepared by combining 45 grams of thepoly(cycloaliphatic carbonate) polyol PC-1667 (from Stahl USA), 20 gramsof the polycarbonate polyol PC-1122 (from Stahl USA), 5 grams of thepolycaprolactone polyol Tone-305, 20 grams of 1,4-butanediol, 0.008grams of dibutyltin dilaurate, 2 grams of the UV light stabilizer CosorbOSG, 1 gram of the UV light stabilizer Tinuvin-292, 30 grams ofpropylene glycol methyl ether acetate, 20 grams of butyl acetate, and 20grams of xylene. The Part B was prepared by combining 75 grams of thedicyclohexylmethane diisocyanate Desmodur W (eq wt=132), 10 grams of thealiphatic polyisocyanate, based on hexamethylenediisocyanate, DesmodurN75 (eq wt=255), and 15 grams of butyl acetate. After Parts A and B aremixed, the resulting solution is coated onto a polyester carrier web andcured according to the following profile: 1 minute at 175° F., 1 minuteat 225° F., 1 minute at 265° F., and 1 minute 285° F. The resultingclear film was about 11-12 microns thick. A thermoplastic polyurethane(caprolactone based polyurethane available as TECOFLEX CLA 93A-V fromNoveon) is extruded into a film having a thickness of 150 microns. Oneside of the resulting extruded film is laminated to the clear filmbetween the nip of a backup roll against a chill roll. The other side ofthe thermoplastic polyurethane film is air corona treated at 4 kilowattsand thermally laminated to a layer of acrylic pressure sensitiveadhesive, releasably adhered on a paper release liner, at 190° F. toform the exemplary polyurethane construction.

From the above disclosure of the general principles of the presentinvention and the preceding detailed description, those skilled in thisart will readily comprehend the various modifications, re-arrangementsand substitutions to which the present invention is susceptible.Therefore, the scope of the invention should be limited only by thefollowing claims and equivalents thereof.

What is claimed is:
 1. A multilayer protective film comprising: a firstlayer comprising a polyurethane, said polyurethane being apolyester-based polyurethane, a polycarbonate-based polyurethane or acombination of both; a second layer comprising a polycaprolactone-basedthermoplastic polyurethane; and a PSA layer comprising a pressuresensitive adhesive, wherein said first layer is bonded to one majorsurface of said second layer and said PSA layer is bonded to an oppositemajor surface of said second layer such that said second layer issandwiched between said first layer and said PSA layer, and saidmultilayer protective film is clear, transparent, and passes the“Staining and Discoloration Test” after being exposed to at least one ofthe fluids from the group consisting of grease, tar, transmission fluid,motor oil, fuel oil, diesel oil, gear oil, and SUNOCO lub/grease.
 2. Thefilm according to claim 1, wherein the polyurethane of said first layeris the reaction product of a polyol and at least an aliphatictriisocyanate, and said polyol is a polyester polyol, a polycarbonatepolyol or a combination of both.
 3. The film according to claim 1,wherein the polyurethane of said first layer is an aliphaticpolyurethane.
 4. The film according to claim 1, wherein the polyurethaneof said first layer is a slightly crosslinked polyurethane that exhibitsat least enough melting or at least enough softening, when heated, toform a bond that passes the “Tape Snap Adhesion Test” after at least oneof the aging conditions (a) Water Immersion in 40° C. water bath for 7days, (b) Fog chamber exposure on a rack at about a 30 degree angle andexposed for 7 days at 38° C. in a chamber with 100% condensation, and(c) Salt spray exposure on a rack at about a 30 degree angle and exposedfor 7 days at 35° C. using a 5% sodium chloride solution in a salt fogchamber.
 5. The film according to claim 1, wherein the polyurethane ofsaid first layer is a solvent-based polyurethane.
 6. A vehiclecomprising a body part having a painted surface protected by saidmultilayer protective film according to claim
 1. 7. The film accordingto claim 1, wherein the polyurethane of said first layer comprises ananionic surfactant.
 8. The film according to claim 7, wherein theanionic surfactant comprises a sulfosuccinate type anionic surfactant.9. The film according to claim 1, wherein the polyurethane of said firstlayer comprises a UV light absorber.
 10. The film according to claim 9,wherein said UV light absorber comprises 2-ethylhexylα-cyano-α-β′diphenylacrylate.
 11. The film according to claim 1, whereinthe polyurethane of said first layer comprises an aziridine crosslinker.12. The film according to claim 1, wherein the polyurethane of saidfirst layer comprises dicyclohexylmethane diisocyanate.
 13. The filmaccording to claim 12, wherein the polyurethane of said first layerfurther comprises an aliphatic polyisocyanate.
 14. The film according toclaim 1, wherein the polyurethane of said first layer comprises apoly(cycloaliphatic carbonate) polyol.
 15. A method of making themultilayer protective film according to claim 1, said method comprising:(a) forming a first layer comprising a polyurethane, the polyurethanebeing a polyester-based polyurethane, a polycarbonate-based polyurethaneor a combination of both; (b) forming a second layer comprising apolycaprolactone-based thermoplastic polyurethane; (c) forming a PSAlayer comprising a pressure sensitive adhesive; (d) bonding one majorsurface of the first layer to one major surface of the second layer; and(e) bonding the PSA layer to an opposite major surface of the secondlayer, wherein the second layer is sandwiched between the first layerand the PSA layer.
 16. The method according to claim 15, wherein saidforming a second layer further comprises: extruding thepolycaprolactone-based thermoplastic polyurethane at an elevatedtemperature through a die to form the second layer.
 17. The methodaccording to claim 16, wherein said bonding the first layer furthercomprises: laminating the one major surface of the first layer to theone major surface of the second layer, after said extruding and whilethe one major surface of the second layer is at an elevated temperaturethat is sufficiently higher than room temperature to facilitate adequatebonding between the first layer and the second layer.
 18. The methodaccording to claim 16, wherein said bonding the first layer furthercomprises: laminating one major surface of the first layer to one majorsurface of the second layer after said extruding and with at least theone major surface of the first layer and the second layer being at atemperature that does not facilitate adequate bonding between the firstlayer and the second layer; and heating the one major surface of thesecond layer to an elevated temperature that is sufficiently higher thanroom temperature to facilitate adequate bonding between the first layerand the second layer during said laminating, wherein said heating occursbefore or during said laminating.
 19. The method according to claim 18,further comprising: releasably laminating an opposite major surface ofthe second layer to a releasable carrier web after said extruding.
 20. Amultilayer protective film comprising: a first layer comprising apolyurethane, said polyurethane being a polyester-based polyurethane, apolycarbonate-based polyurethane or a combination of both; a secondlayer comprising a polycaprolactone-based thermoplastic polyurethane;and a PSA layer comprising a pressure sensitive adhesive, wherein saidfirst layer is bonded to one major surface of said second layer and saidPSA layer is bonded to an opposite major surface of said second layersuch that said second layer is sandwiched between said first layer andsaid PSA layer, adhesion between said first layer and said second layerpasses the “Tape Snap Adhesion Test”, said multilayer protective filmpasses the “Staining and Discoloration Test”, and said first layer hasan exposed major surface with the appearance of having been cast onto asmooth major surface of a releasable carrier web, dried and the carrierweb removed.
 21. The film according to claim 20, wherein said film iscolored.
 22. A method of making the multilayer protective film accordingto claim 20, said method comprising: (a) forming a first layercomprising a polyurethane, the polyurethane being a polyester-basedpolyurethane, a polycarbonate-based polyurethane or a combination ofboth; (b) forming a second layer comprising a polycaprolactone-basedthermoplastic polyurethane; (c) forming a PSA layer comprising apressure sensitive adhesive; (d) bonding one major surface of the firstlayer to one major surface of the second layer; and (e) bonding the PSAlayer to an opposite major surface of the second layer, wherein thesecond layer is sandwiched between the first layer and the PSA layer.23. The method according to claim 22, wherein said forming a first layerfurther comprises: coating an aqueous-based or solvent-basedpolyurethane dispersion onto the releasable carrier web.
 24. A method ofmaking a multilayer protective film, said method comprising: forming afirst layer comprising a polyurethane, the polyurethane being apolyester-based polyurethane, a polycarbonate-based polyurethane or acombination of both; forming a second layer comprising apolycaprolactone-based thermoplastic polyurethane by extruding thepolycaprolactone-based thermoplastic polyurethane at an elevatedtemperature through a die to form the second layer; forming a PSA layercomprising a pressure sensitive adhesive; bonding one major surface ofthe first layer to one major surface of the second layer by laminatingone major surface of the first layer to one major surface of the secondlayer after said extruding and with at least the one major surface ofthe first layer and the second layer being at a temperature that doesnot facilitate adequate bonding between the first layer and the secondlayer, and heating the one major surface of the second layer to anelevated temperature that is sufficiently higher than room temperatureto facilitate adequate bonding between the first layer and the secondlayer during said laminating, with said heating occurring before orduring said laminating; bonding the PSA layer to an opposite majorsurface of the second layer; releasably laminating an opposite majorsurface of the second layer to a releasable carrier web after saidextruding; exposing the opposite major surface of the second layer,after said releasably laminating; and corona treating the opposite majorsurface of the second layer, after said exposing and before said bondingthe PSA layer, wherein the second layer is sandwiched between the firstlayer and the PSA layer.